Fuel injection systems are typically used to inject a fuel spray into an inlet manifold or a combustion chamber of an engine. Fuel injection systems have become the primary fuel delivery system used in automotive engines, having almost completely replaced carburetors since the late 1980s. Fuel injectors used in these fuel injection systems are generally capable of two basic functions. First, they deliver a metered amount of fuel for each inlet stroke of the engine so that a suitable air-fuel ratio can be maintained for the fuel combustion. Second they disperse the fuel to improve the efficiency of the combustion process. Conventional fuel injection systems are typically connected to a pressurized fuel supply, and the fuel can be metered into the combustion chamber by varying the time for which the injectors are open. The fuel can also be dispersed into the combustion chamber by forcing the fuel through a small orifice in the injectors.
For example, diesel fuel is a petrochemical derived from crude oil. It is used to power a wide variety of vehicles and operations. Compared to gasoline, diesel fuel has a higher energy density (e.g., 1 gallon of diesel fuel contains ˜155×106 J, while 1 gallon of gasoline contains ˜132×106 J). For example, most diesel engines are capable of considerably higher fuel efficiency as a result of operation direct-injection of fuel to produce stratified charge combustion into unthrottled air that has been sufficiently compression heated to provide ignition of diesel fuel droplets, as compared to gasoline engines, which are operated with throttled air and homogeneous charge combustion to accommodate such spark plug ignition related limitations. However, while diesel fuel emits less carbon monoxide than gasoline, it emits for nitrogen based emissions and small particulates that can produce global warming, smog and acid rain along with serious health problems such as emphysema, cancer and cardiovascular diseases.